1. Field of the Invention
The present invention relates generally to chemical mechanical polishing (CMP) compounds and methods and post CMP cleaning solutions and methods, and particularly to the polishing and cleaning of CoFeNi structures such as magnetic poles fabricated within alumina fill layers during magnetic head fabrication.
2. Description of the Prior Art
Magnetic heads for devices such as hard disk drives typically include magnetic pole structures that are utilized to generate magnetic fields for writing magnetic data bits into the magnetic media of a hard disk of a hard disk drive. Such magnetic poles are typically comprised of NiFe. In a typical prior art magnetic pole fabrication process, utilizing photolithographic techniques, a magnetic pole structure is electroplated within a trench that is photolithographically formed within a photoresist layer. Following the electroplating of the magnetic pole piece, the photoresist is removed, such as with the use of a chemical stripper, and a layer of alumina is then deposited to fill the field surrounding the electroplated pole piece. Thereafter, a chemical mechanical polishing (CMP) step is typically undertaken to create a flat surface for subsequent magnetic head fabrication steps.
In such a CMP step it is desirable that the polishing be accomplished such that the material removal rate of the alumina and the NiFe pole piece be approximately equal, such that a flat polished surface is obtained. Where the material removal rate of either the alumina or the NiFe pole piece differs, an undesirable step will be created at the surface interface of the alumina and NiFe pole piece.
A CMP processing step involves the use of a polishing slurry including abrasive particulates and liquid components that typically include water, a corrosion inhibitor such as BTA (1H-benzotriazole) and an oxidizer such as ammonium persulfate (APS). A biocide chemical is typically added to prolong the shelf life of the polishing compound. In the prior art for NiFe pole structures a polishing slurry is utilized where the material removal rate of the NiFe pole piece and alumina field are approximately equal, such that no undesirable polishing steps are created.
Following a CMP step it is necessary to clean the polished wafer surface to remove all traces of polishing slurry and particulates. A typical prior art cleaning solution for a wafer having NiFe magnetic pole pieces is ammonium citrate or hydrogen peroxide into which the wafer is dipped for cleaning. Following wafer cleaning, the wafer is rinsed in deionized (DI) water to remove any remaining cleaning solution from the wafer.
Hard disk drives that are currently being developed include data disks having significantly increased areal data storage densities. Smaller magnetic pole structures are necessary to write the smaller magnetic data bits of the higher density data disks, and the high moment magnetic material CoFeNi (2.45 Tesla) recently is being considered for replacing NiFe as a pole material to increase the ability for high density writing. However, CoFeNi is more chemically active than NiFe. With current existing NiFe CMP processes, the chemical attack upon the CoFeNi is very strong and causes serious corrosion of the CoFeNi surface. Also, the polishing of the CoFeNi and alumina is uneven, and unwanted steps are created between the surfaces of the CoFeNi and the alumina when prior art CMP slurries and parameters for NiFe are utilized when polishing the CoFeNi magnetic poles. Additionally, it has been found that the prior art ammonium citrate cleaning solutions also cause unwanted corrosion of the CoFeNi magnetic pole pieces.
There is therefore a need for new polishing and cleaning formulations for use with CoFeNi magnetic pole structures in the fabrication of magnetic heads.